Is it possible to simply replace the clutch with a torque converter? I know you could operate in one gear that way, but could you shift (manualy) while under way or would that lock the converter?
John
John
Automatic ZF?
- Thread starter toy264
- Start date
Chris Kouba
Supporter
John,
There may be others out there who can answer this better but going from manual to auto isn't as simple as swapping in a TC. I will take a stab at it with my small arsenal of info on the subject and maybe someone else can fill in the gaps (or correct the errors).
The reason a TC works in an auto box is the gear set. They are planetary gears, meaning they are ALWAYS engaged and the ratios are changed by allowing different portions of the gearset to turn or remain fixed relative to each other or the gearbox. This is what all the clutch bands do and is why your box won't shift correctly if your bands are slipping.
In the manual box, the individual speeds are always engaged but the collars locking the gears together are free spinning until the shift fork locks them to the output shaft. This is a little difficult for me to describe succinctly but I am certain someone else could probably do it better.
Where this is all going is with the TC, the engine is always spinning the input shaft and it only "disengages" once the motor is below its stall speed. Disengagement is not a completely correct description as there is probably too much residual fluid friction for the input shaft to truly be idled and would likely continue to be spinning at whatever RPM the motor is running. This would not make for very smooth shifting of gears in a synchro-based box.
For a manual, the clutch physically disconnects the motor from the box and as the shift fork engages the locking collar for the selected gearset, the synchros get everything to match speeds before they click together at whatever road speed the vehicle is traveling. Leads to nice smooth shifts and easy on the drivetrain.
The interesting concept going through my mind now though would be a TC-equipped "dog box." The dog box style gearboxes have relatively enormous lobes (compared to synchros) which enable them to be shifted without using the clutch. You simply lift off the gas to relieve the pressure on the dogs and slam the shifter from gear to gear and the large, strong dog ear-shaped lobes engage the desired raios at will (at least that's what I understand, never having driven one). I'm not sure if you have to match revs to downshift, but I imagine it'd be pretty awkward if you didn't. It's much more of a competition box and I'm pretty certain the dogs don't exactly have a warranty or a 100k mile life expectancy...
Where this thought is going though is possibly with a dog box, the TC would let you idle and shift as well. Not too sure how it'd really work though but it'd be really interesting. You would likely need to always have a gear engaged though as if you went from unrestrained idle to selecting first gear it might get expensive quickly.
Anybody have any experience out there?
Chris
There may be others out there who can answer this better but going from manual to auto isn't as simple as swapping in a TC. I will take a stab at it with my small arsenal of info on the subject and maybe someone else can fill in the gaps (or correct the errors).
The reason a TC works in an auto box is the gear set. They are planetary gears, meaning they are ALWAYS engaged and the ratios are changed by allowing different portions of the gearset to turn or remain fixed relative to each other or the gearbox. This is what all the clutch bands do and is why your box won't shift correctly if your bands are slipping.
In the manual box, the individual speeds are always engaged but the collars locking the gears together are free spinning until the shift fork locks them to the output shaft. This is a little difficult for me to describe succinctly but I am certain someone else could probably do it better.
Where this is all going is with the TC, the engine is always spinning the input shaft and it only "disengages" once the motor is below its stall speed. Disengagement is not a completely correct description as there is probably too much residual fluid friction for the input shaft to truly be idled and would likely continue to be spinning at whatever RPM the motor is running. This would not make for very smooth shifting of gears in a synchro-based box.
For a manual, the clutch physically disconnects the motor from the box and as the shift fork engages the locking collar for the selected gearset, the synchros get everything to match speeds before they click together at whatever road speed the vehicle is traveling. Leads to nice smooth shifts and easy on the drivetrain.
The interesting concept going through my mind now though would be a TC-equipped "dog box." The dog box style gearboxes have relatively enormous lobes (compared to synchros) which enable them to be shifted without using the clutch. You simply lift off the gas to relieve the pressure on the dogs and slam the shifter from gear to gear and the large, strong dog ear-shaped lobes engage the desired raios at will (at least that's what I understand, never having driven one). I'm not sure if you have to match revs to downshift, but I imagine it'd be pretty awkward if you didn't. It's much more of a competition box and I'm pretty certain the dogs don't exactly have a warranty or a 100k mile life expectancy...
Where this thought is going though is possibly with a dog box, the TC would let you idle and shift as well. Not too sure how it'd really work though but it'd be really interesting. You would likely need to always have a gear engaged though as if you went from unrestrained idle to selecting first gear it might get expensive quickly.
Anybody have any experience out there?
Chris
Ian Anderson
Lifetime Supporter
Gents
It was suggested earlier that a hand operated Clutch may be possible but the pressure required may not be possible without assistance.
A long shot but would a brake booster servo work well enough to transfer he pressure exerted on a hand master cylinder to enough pressure / flow to move the slave?
I have no idea but it may be a slightly easier route
Ian
It was suggested earlier that a hand operated Clutch may be possible but the pressure required may not be possible without assistance.
A long shot but would a brake booster servo work well enough to transfer he pressure exerted on a hand master cylinder to enough pressure / flow to move the slave?
I have no idea but it may be a slightly easier route
Ian
Here is a Chaparral 2 speed auto transaxle. http://www.can-am-cars.com/productcart/pc/viewCat_P.asp?ProdSort=1&idCategory=4&page=2&iPageSize=3
Aarughhh. Exactly what I need and $5000 more than I could possibly afford. However, it's good to see what one actually looks like, should my ship ever come in! Thanks, Andy!
Chris- Your explanation made perfect sense- I misunderstood how the TC and automatic planetary function together. Thank you for taking the time to explain.
Looking at the pic of the Chaparral transaxle, is the flange facing the camera what the half shaft bolts up to? Jeez, massive isn't the word!
Chris- Your explanation made perfect sense- I misunderstood how the TC and automatic planetary function together. Thank you for taking the time to explain.
Looking at the pic of the Chaparral transaxle, is the flange facing the camera what the half shaft bolts up to? Jeez, massive isn't the word!
I don't have a clue. I was just reading your thread a few days ago and today happened across the transaxle ad. I figured it must be some kind of divine intervention, because I wouldn't think one could be found without a Chaparral attached to it!
Andy
Andy
Ian-
Not being familiar with the Porche transaxles, I'm not sure whether there is a suitable bell housing to match up with the 289, and re-engining the car is beyond my skills. That being said, if a paddle shift switch could be positioned on the hand control arm, operating it with the left thumb would not be difficult (that's where the horn switch lives now).
John
Not being familiar with the Porche transaxles, I'm not sure whether there is a suitable bell housing to match up with the 289, and re-engining the car is beyond my skills. That being said, if a paddle shift switch could be positioned on the hand control arm, operating it with the left thumb would not be difficult (that's where the horn switch lives now).
John
John
You can have a torque converter instead of a clutch.
Back in the 80s I was fitting a lot of 2nd hand motors into Mazda rotories.
I was buying import engines 13bs out of I think rx5s.
They had the set up you are looking for.
The torque converter was called a fluid flywheel.
It was cast alloy & could be pulled apart.It had bolts all the way around the outside.
The rotaries have a plug in the back of the eccsentric shaft ( crank)this is removed & the flywheel is supplied by engine oil through the centre of the fluid flywheel(there was 2 orings on the snout) & it drained out through a gallery that was cast into the bell housing & went back to the rear of the engine & drained into the sump.
These engines the oil pressure was no higher than normal.
The gearbox didnt look to different from a normal box, it splined into the rear of the ffwheel.
I cant remember how they sealed of the box to the ffwheel exactly as it has been 20years or so.
I dont recollect a slave cylinder but that whould be worth checking.
Aparantly they were only in Japan due to heavy traffic .
You should look up Mazda on the net RX5 fluid flywheel ect ect.
Hope this will get you a little closer.
Jim /ubbthreads/images/graemlins/smile.gif
You can have a torque converter instead of a clutch.
Back in the 80s I was fitting a lot of 2nd hand motors into Mazda rotories.
I was buying import engines 13bs out of I think rx5s.
They had the set up you are looking for.
The torque converter was called a fluid flywheel.
It was cast alloy & could be pulled apart.It had bolts all the way around the outside.
The rotaries have a plug in the back of the eccsentric shaft ( crank)this is removed & the flywheel is supplied by engine oil through the centre of the fluid flywheel(there was 2 orings on the snout) & it drained out through a gallery that was cast into the bell housing & went back to the rear of the engine & drained into the sump.
These engines the oil pressure was no higher than normal.
The gearbox didnt look to different from a normal box, it splined into the rear of the ffwheel.
I cant remember how they sealed of the box to the ffwheel exactly as it has been 20years or so.
I dont recollect a slave cylinder but that whould be worth checking.
Aparantly they were only in Japan due to heavy traffic .
You should look up Mazda on the net RX5 fluid flywheel ect ect.
Hope this will get you a little closer.
Jim /ubbthreads/images/graemlins/smile.gif
